This invention relates to ambient temperature rechargeable lithium battery systems.
Rechargeable lithium batteries are useful in many applications because of their high battery voltage and high capacity per unit weight and volume. U.S. Pat. No. 4,304,825 issued to Basu describes a battery which has a conventional positive electrode, a molten salt electrolyte and a negative electrode comprising lithium intercalated graphite. This type of battery structure has proven to be very effective in many applications which involve high temperature operation. However, it is desired in many cases to have a battery that can operate at ambient temperature and still exhibit a high battery voltage and high capacity per unit weight and volume.
Secondary (rechargeable) lithium batteries which operate at ambient temperature typically include a lithium anode, an organic electrolyte and a cathode. This type of battery structure is generally known from U.S. Pat. No. 4,035,555 issued July 12, 1977 to D. W. Murphy and F. A. Trumbore. Such a battery cell exhibits a high capacity per unit weight and volume as well as extensive rechargeability. However, the lithium anode in such a structure may undergo a slow chemical change thereby limiting the battery's cycle life. For many commercial applications employing rechargeable batteries, a battery which can withstand an ever greater number of discharge-charge cycles is desired.
Accordingly, it is a primary objective of the present invention to provide a rechargeable lithium battery which can maintain a high capacity after many discharge-charge cycles.